Lever Rule: Summary

The answer to the ConcepTest is given below and will open in a separate window. 
Key points from this module:
  • The lever rule is a way to represent a mass balance for two phases in equilibrium.
  • The lever rule applies to any two phases in equilibrium for a binary system: liquid-liquid, solid-solid, solid-liquid, and liquid-vapor.
  • The lever rule also applies to a single-component system to determine the amounts of vapor and liquid in equilibrium (e.g., on a pressure-volume diagram).
From studying this module, you should now be able to:
  • Apply the lever rule to any system that has two phases in equilibrium.
Prepared by John L. Falconer, Department of Chemical and Biological Engineering, University of Colorado Boulder